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Link between past and present - the yeast

Mate Farkas
29/09/2022 14:09
Link between past and present - the yeast

Brewer's yeast is not only an essential part of our favorite beverage, but it also played a significant role in the development of human civilization. But what makes Saccharomyces cerevisiae, commonly known as baker's yeast, so special?

What connects the modern society running on space technology to the first human settlements? Fermentation! Artifacts connected to alcoholic drinks dating back to thousands of years prove that once humans settled down, they started fermenting stuff. In fact, there is a theory that the first settlements and agriculture in general were started out by people who wanted to get a reliable source of alcohol! Think about it; it was probably no cakewalk to protect your half-domesticated crop from the nomadic hunter-gatherers, who would probably bash your skull in for the free food that you worked on the whole year for with your primitive tools. That’s why researchers say that there must have been something extra to settling down, to make it a worthwhile endeavor. And this extra might well have been alcoholic fermentation! The ever-exploring hunter societies were pretty well accustomed to living off of the woods. They probably met animals acting tipsy after eating rotting fruit off the ground, and the curious among them most likely tasted them too, feeling the delirious effects afterwards. Since fruits and other fermentables are location dependent, the club-wielding cavemen looking for a buzz had to make some sacrifices to their ability to move freely after herds of game. Not to mention that fruit left to itself tends to rot more than ferment cleanly, and areas where the microclimate promotes the latter are not common either. 

Gene sequence research proves that Saccharomyces cerevisiae, also known as baker's yeast, the ancestor of one of the most common microbes responsible for alcoholic fermentation, is also responsible for the first European and Asian wines! The reproduction of S. cerevisiae is special. It is a polyploid organism, meaning its cell contains 3-4 copies of its gene pool (while human diploid cells contain 2x23 chromosomes, and the cells responsible for reproduction contain only 1x23). This special characteristic helped it to remain relatively isolated from similar yeasts during its development over thousands of years, and to develop the properties that made it one of the most important industrial microorganisms of mankind. And this isolation also made it possible to examine its spread over the globe, which was made possible by the introduction of long distance trade by the first ever civilizations.

Albeit its presence going back thousands of years has been confirmed, yeast was only first observed by Antonie van Leeuwenhoek in the late 1600s, although he had not yet defined it as a living organism. At the end of the 18th century, it was already suspected that small organisms found on the skin of grapes could be responsible for fermentation. This assumption was proven by Louis Pasteur in his work published in 1857. He realized that yeast multiplies in an environment rich in oxygen, where the volume of the living mass increases, while it performs alcoholic fermentation in an oxygen-free environment. All that was left to figure out before industrial introduction could begin was the method of producing pure (mono) cultures. By the end of the 19th century, thanks to the work of Robert Koch and Julius Richard Petri, this milestone was reached, making it possible for modern industry to put fermentation, which has a tradition of thousands of years, on a scientific basis instead of relying on empirical methods. And that's how we got from the first alcohol induced beauty sleep enjoying gatherer to the modern industrial workhorse. Although our lives are immeasurably far from those of our ancestors, there is still a link that connects us!